The invention relates to vehicle seats. Disclosed herein are embodiments of vehicle seats that reduce the load on occupants during a rear-end collision.
During a rear-end collision, where the rear of a vehicle such as an automobile is impacted, the vehicle experiences a large collision while traveling in reverse, or the like, there is a risk that the neck region (neck) of an occupant will receive a large load. Generally speaking, the primary cause of such a load is that the head region alone suddenly moves backward relative to the chest region of the seated occupant, which causes the neck region to bend to an excessive degree. In other words, during a rear-end collision, a load is placed on the neck region due to the head region of the seated occupant tilting backward suddenly from inertia.
Accordingly, vehicle seats in automobiles and the like have conventionally been provided with headrests, located on the upper area of the seat back (seating portion), that support the head region of the occupant in order to protect the head region, neck region, and so on of the occupant from impacts during rear-end collisions to reduce the load on the neck region.
However, it is difficult for a headrest installed in a fixed state to prevent the head region from sudden backward movement during a rear-end collision. In other words, unless the head region of the occupant is supported by quickly reducing the gap between the head region and the headrest when a rear-end collision occurs, there are cases where the head region will suddenly move backward, and the load exerted on the neck region cannot be reduced sufficiently as a result.
To solve this problem, active headrests have been proposed, in which, during a rear-end collision, the backward movement of the load of the occupant is utilized, so that the headrest is moved forward in order to support the head region of the occupant and suppress the load exerted on the neck region (see, for example, Japanese Patent Document No. 2003-341402 (“the '402 patent Document”)).
Furthermore, a technique has been proposed where, in a vehicle seat provided with a seat back that supports a seat back cushion using a seat back frame including side frames, a pressure receiving member is installed by providing mobile link members between the side frames; when a large impact load is exerted on an occupant during a rear-end collision, the link members pivot and the pressure receiving member is moved backward, which causes the occupant to sink toward the seat back, or in other words, toward the rear, thus bringing the head region closer to the headrest (see, for example, Japanese Patent Document No. 2009-023517 (“the '517 patent Document”)).
With the technique disclosed in the '402 patent Document, when the occupant moves backward due to inertia during a rear-end collision, the load of the occupant is exerted on a mobile plate provided in the rear of the seat, and the headrest moves forward in tandem with the mobile plate moving backward, thus dissipating the load exerted on the occupant.
As described above, with the technique disclosed in the '402 patent Document, the occupant moves backward during a rear-end collision, and at that time, the load is received by the mobile plate; the headrest is moved forward in tandem with backward movement of the mobile plate.
On the other hand, with the technique disclosed in the '517 patent Document, the pressure receiving member is attached to the side frames of the seat via the link members, and when a rear-end collision occurs, the pressure receiving member moves significantly backward under the load of the occupant. This configuration allows the upper body of the occupant, including the lower back region, to sink into the seat back without the headrest moving forward, and thus the head region and back are simultaneously supported by the headrest and the seat back, respectively; this prevents the head region from suddenly moving backward and thus makes it possible to reduce the burden on the neck region.
In this manner, the stated the '402 patent Document and the '517 patent Document disclose vehicle seats provided with configurations in which the head region or the neck region is supported from behind by the headrest by causing the back of the occupant to sink backward during a rear-end collision. These techniques have merits in that they make it easy for the head region of the occupant to make contact with the headrest by causing the back region of the occupant to sink backward, which prevents the head region from suddenly moving backward.
If, when a rear-end collision has occurred, the upper body of the occupant can be tilted backward integrally, or in other words, if the head region, neck region, and torso region can be tilted backward while maintaining the relative positions therebetween, the head region will not move backward by itself. This makes it possible to suppress the burden on the neck region, but in the stated techniques, the seat back restricts the backward movement of the torso region of the occupant. Accordingly, because the amount of backward movement of the connection point between the neck region in the torso region relative to the amount of backward movement of the head region is suppressed, there has been a risk that the angle at the connection location between the head region and the neck region has changed between when normally sitting and when a rear-end collision has occurred, placing a burden on the neck region.
With techniques such as that disclosed in '402 patent Document, in which the headrest moves to make contact with the head region of the occupant, it is necessary to provide a separate movement mechanism for the headrest in order to cause the headrest and the pressure receiving member to move in tandem, which is problematic in that it not only complicates the structure and increases costs, but also increases the weight of the seat as a whole. It has also been necessary to provide a mobile portion in the seat back frame for moving the headrest, which has been problematic in that it reduces the rigidity of the frame.
With the technique disclosed in the '517 patent Document, the mechanism for attaching the pressure receiving member to the side frames is complicated, and there is a problem in that a large number of components is required to attach the pressure receiving member.